The current invention is generally related to inventory and management of articles or items, and more particularly related to enhanced detection of the article placement at predetermined positions in a predetermined area as well as prevention of the removal of these articles from the predetermined area.
IC cards used as a non-contact identification tag have been used in combination with a reader-writer for managing articles. For example, IC cards have been used in transportation systems as well as goods distribution systems with a frequency band of 13.56 MHz. The reader-writer is equipped with an antenna which periodically transmits power as well as question data and receives a response signal from the IC cards that are located within a reception range of the above transmission.
Another prior art example of the article managing system is library management systems. As shown in FIG. 1, one exemplary library management system utilizes a bar code identification tag 12 on library books 10. Each bar code encodes information on book identification, a title, classification/category, author and so on. FIG. 2 shows a membership card 14 used in conjunction with the above book identification bar code 12 of FIG. 1. A membership bar code 16 includes information on a name of the member, address, a telephone number, a driver license number and so on. Both of the bar codes 12 and 16 are read by a bar code reader when a member checks out a book to generate a borrowing record in a central computer. The borrowing record includes the book identification, the title, the publisher, the member identification, a check-out date, a return due date and a returned date. When the book is returned, the bar code on the returned book is read again to write the actual returned date in the borrowing record.
In stead of using the bar codes, Japanese Patent Publication Hei 11-79328 discloses the use of IC cards in a library management system. An IC card is placed on each book, and each IC card holds information to identify the books. The IC card does not contain any battery, but the information can be read and written by a reader-writer. A bottom surface of a shelf is equipped with a coil or antenna of the reader-writer. The coil or antennas include a pair of a transmission coil and a reception coil that are alternately wound on a flat line. When a book is inserted into the shelf over the flat coil antenna, the information stored in the IC card is detected by the reader-writer via the antenna. Although the coil antennas are redundantly placed in parallel or a predetermined geometry on a shelf surface, the communication between the IC card and the reader-writer partially depends upon a relative angle of the book with respect to the antenna coil. More precisely, since the magnetic field directions of the IC card and the antenna coils are not often perpendicular with each other upon insertion of the book into the self, the communication is not optimal.
The communication between the IC card and the reader-writer remains to be improved. As shown in FIG. 3, when books 10A and 10B respectively with the IC card tags 90A and 90B is near an exit detection device 140, the detection is accomplished with sufficiency with a certain predetermined relative directionality. The IC card 90A is placed in the back of the book 10A while the IC card 90B is placed on a front cover of the book 10B. In order for the book 10A to be sufficiently detected, the book 10A must be placed perpendicular to the exit gate 140 so that the magnetic field direction of the IC card tag 90A as indicated by a double headed arrow is also perpendicular. On the other hand, in order for the book 10B to be sufficiently detected, the front cover 10B of the book 10B has to face the exit detection device 140 as shown in FIG. 3 so that the magnetic field direction of the IC card tag 90B as indicated by a double headed arrow is also perpendicular.
In order to solve the above and other problems, according to a first aspect of the current invention, a method of keeping track of a plurality of articles in a predetermined area, including: placing a non-contact id tag on one surface of each of the articles to be monitored, the non-contact id tag containing information; placing a sensing portion of a non-contact id tag reader-writer at a predetermined location within the predetermined area; placing a non-contact id tag detection enhancing device so as to increase detection of the non-contact id tag by the non-contact id reader-writer; and detecting the non-contact id tag near the non-contact id reader-writer in the predetermined area.
According to a second aspect of the current invention, a system for keeping track of a plurality of articles in a predetermined area, including: a non-contact id tag placed on one surface of each of the articles to be monitored, the non-contact id tag containing information; a non-contact id tag reader-writer located near the predetermined area, the non-contact reader-writer having a sensing portion for detecting the non-contact id tag placed near the non-contact id reader-writer; and a non-contact id tag detection enhancing device also placed near the non-contact id reader-writer so as to increase the detection of the non-contact id tag by the non-contact id reader-writer.
According to a third aspect of the current invention, a non-contact id tag module, including: an IC card tag having a memory unit for storing information, a control unit connected to the memory unit for reading and writing the information, a resonance circuit for resonating a signal, a power generating unit connected to the resonance circuit for generating power from the signal, and a data demodulation unit and a data modulation unit for connected to the control unit for respectively modulating and demodulating the information to generate the signal; and a loop conductive line for enhancing reception and transmission of the signal.
According to a fourth aspect of the current invention, a storage shelf unit for detecting a non-contact id tag on articles, including: a plurality of shelves; a plurality of movable loop antennas placed on the shelves for transmitting signals to and receiving signals from the non-contact id tag; an antenna switcher connected to the movable loop antennas for switching from one of the movable loop antennas to another one of the movable loop antennas; a data modulator/demodulator connected to the antenna switcher for modulating and demodulating the signals; a processing unit connected to the data modulator/demodulator for processing the signals; and a communication interface connected to the processing unit for providing an interface in transmitting the processed signals and in receiving other signals from an outside unit.
According to a fifth aspect of the current invention, an exit monitor device for detecting a non-contact id tag on articles, including: a plurality of pairs of loop antennas placed near an exit for transmitting signals to and receiving signals from the non-contact id tag, each of the pairs of the loop antennas having magnetic field directions that are perpendicular to each other; an antenna switcher connected to the loop antennas for switching from one of the pairs of the loop antennas to another one of the pairs of the loop antennas; a data modulator/demodulator connected to the antenna switcher for modulating and demodulating the signals; a processing unit connected to the data modulator/demodulator for processing the signals; and communication interface connected to the processing unit for providing an interface in transmitting the processed signals and in receiving other signals from an outside unit.